Basic Chemistry

Vocabulary Atoms: Smallest particle of an element that has all the properties of matter (anything that occupies space and has mass): Protons- particles in the nucleus with positive charge Electrons- particles orbiting around nucleus with negative charge Neutrons- particles in the nucleus with no charge (neutral)

Vocabulary Elements: Simplest form of a pure substance Molecule: when two or more atoms join together (ex O2) Compounds: Two or more different elements chemically combined to form a new substance (ex. NaCl – sodium chloride, table salt)

Counting Atoms

Periodic Table Many elements with some some directly needed and some not

Trace Elements Elements that are essential for an organism to live but only in small amounts Different organisms require different trace elements

Trace Elements Some examples: Sometimes added to ‘fortified foods’ Iron (Fe) critical to transport oxygen in blood Iodine (I) is important for producing a hormone (iodized salt) Flourine (F) helps reduce tooth decay Sometimes added to ‘fortified foods’

Quick Search

Periodic Table Lots of numbers, what do they mean?

Using the Periodic Table Atomic Number Equal to # protons = # electrons Periodic Table is arranged by this number Symbol “Shorthand” for the element – Note 2nd letter is always lowercase Atomic Mass Number Total AVERAGE mass of Protons + Neutrons + Electrons 17 Cl 35.5

Isotopes An isotope is a variation of an element (same protons) but can have diff. # of neutrons

Radioactive Isotopes An isotope that is unstable and decays, spontaneously giving off particles and energy Can be damaging to living organisms Can break apart DNA and other molecules, or change the chemical bonds Can be used to help Radioactive dating Tracers

Radioactive tracers are frequently used in medical diagnosis. Sophisticated imaging instruments are used to detect them. An imaging instrument that uses positron-emission tomography (PET) detects the location of injected radioactive materials Student Misconceptions and Concerns • The dangers posed by certain chemicals in our food and broader environment have sometimes misled people to associate chemicals with harm. People might not want chemicals added to their food or in their environment. Students often fail to appreciate the chemical nature of our bodies and our world and the potential harm or benefits of naturally occurring chemistry. They often fail to understand why “natural” does not necessarily mean good. (Consider presenting a long list of naturally occurring toxins to make this point.) Your class may benefit from a class discussion of these misconceptions about our attitudes toward chemicals. Teaching Tips • The half-lives of many radioactive substances, especially those used for dating fossils, might lead some students to expect very long periods of decay for any radioactive substance. This might even be alarming if students are someday asked to consume a radioactive substance for a medical test. However, some medically significant isotopes have relatively short half-lives. Radioactive iodine-131 is often used to diagnose or treat certain thyroid problems. Its half-life of eight days means that it will decay quickly. • Depending upon where you are teaching, radon in homes may be a common problem and pose a significant health risk. If you are in a high-radon region, consider adding details about home remediation methods and expenses or have students research the topic and report back.

https://www.youtube.com/watch?v=cKJMk2Oiod0

Valence Electrons An electron on the outermost energy shell of an atom Important to understand because this is a key factor in how atoms will BOND with each other Octet rule – stable atom will have 8 electrons in that outer shell, atoms ‘want’ 8 electrons, they ‘want’ to be stable

1 2 # of Valence Electrons 3 4 5 6 7 8

Types of Chemical Bonds Covalent- Two elements bond by sharing electrons (strongest bond type)

Animation: Covalent Bonds

Types of Chemical Bonds Ionic- Two elements bond by transferring electrons to create ions that attract together (+ is attracted to - after an electron is transferred)

Animation: Ionic Bonds

Water Model Each students should take a water molecule model. Look at it, hold it. Examine how it interacts with other student’s water molecules? What is holding the hydrogens to the oxygen? How can the water molecules connect together? What is different about these two bonds?

Penny and water droplets Move to the back of the room to where there is a penny. Take a pipet and put one drop of water on the penny. Predict how many droplets will fit on the penny. Next put as many droplets on the penny as you can.

Types of Chemical Bonds Hydrogen – Important bond for biology. A molecule with an uneven charge on it, will bond to another unevenly charged molecule

Animation: Water Structure and Hydrogen bonds

http://www.flixxy.com/water-drop.htm

Polarity Some electrons are not shared evenly in covalent bonds. One end, or pole, of the molecule has a partial negative charge while the opposite pole has a partial positive charge.

Polarity Poles attract opposite charges – polar substances dissolve in water Nonpolar substances do not dissolve in water Important with molecules trying to pass through a membrane Polar head Non-polar tail